NEW YORK — If someone told you of a barnstorming TV host who interviewed people around the country about a given subject, you'd say it sounds like a lot of the road-trip reality series that have proliferated on cable TV.

But what if that host had NPR credentials? And what if the show's theme wasn't burger stands or pawn brokers but the most important document in the history of self-governance?

Then it might sound a little more like "Constitution USA," a four-part nonfiction series that debuts Tuesday on PBS (KOCE locally) and hosted by NPR personality Peter Sagal, who on the news-quiz show "Wait Wait … Don't Tell Me!" has been practicing a kind of nerd-fun aesthetic for 15 years.By offering a tour through key legal questions and their geographic hotbeds, "Constitution USA" essentially attempts to do for American jurisprudence what Guy Fieri has done for cheesesteaks and hash browns.

"I don't think Guy Fieri invented the road trip story," Sagal said wryly when presented with the comparison. "That one probably goes back to Homer."

Like that quote, "Constitution USA" provides an inkspot of sly humor and a quill's worth of good-for-you education. As he walks through a park here explaining his new PBS hybrid, Sagal, 48, points out how we're surrounded by constitutional issues — the surveillance cameras that raise privacy questions, or a building knocked down to widen the park that represents a case study in eminent domain.

A similar spirit permeates Sagal's on-camera adventures, which has him traveling from Mendocino, Calif., to New Haven, Conn., to find people whose lives have been affected by the country's legal blueprint. In the first episode, which focuses on the tension between states' rights and federal powers, we watch:

• A Northern California pot grower caught between federal law, which restricts his activities, and California law, which allows them.

• A meeting between a member of the so-called "Little Rock Nine" and the troop who escorted her into a previously all-white school at the dawn of integration in 1957, illustrating the constitutional underpinnings of the civil rights movement.

• Sen. Rand Paul (R-Ky.) complaining about the federal government's interest in mandating the type of toilet he can install in his home, as a way for Sagal to examine the parameters of the commerce clause.

In all of these cases the show illuminates its point less by infographics and somber talking heads — though there is a dollop of that too — than by finding colorful people whose stories illuminate the issues. Ultimately the goal is to explain cases such as 1803's Marbury vs. Madison (which, if it's been awhile since your last Con Law lesson, established the principle of judicial review) to Brown vs. Board of Education (the 1954 case overturning segregation) and Wickard vs. Filburn (the 1942 ruling that allowed the federal government to regulate economic activity).But it seeks to do that with a degree of human drama and idiosyncrasy.

"We didn't want to do the traditional PBS documentary — you know the one, where David McCullough is narrating and there are a lot of important facts ticked off and then everybody falls asleep," Sagal said. "We wanted to do something fun."

It's not always an easy balance. When Sagal thought he'd get a little bawdy (by public-airwaves standards) in Las Vegas by setting a segment about the 1st Amendment at a strip club — "no strippers, just me, a nice couch and maybe a pole in the background" — he ran into network resistance and had to scrap the idea. (He later admitted that was probably the right choice. "Uh, yes, Mr. Congressman, the reason we were at this strip club, you see…" he said, leaning in to an imaginary mike and clearing his throat in imitation of a PBS executive at a congressional hearing.)

As he does on "Wait Wait," Sagal mixes one-liners with a kind of endearing pedantry. (On the NPR show, the Chicago-based host banters with callers and comedian guests about current events; a few days after the interview, he'll be on an NYU stage for a live movie-theater simulcast of the show, where he'll trade barbs with comedians such as Steve Martin and Paula Poundstone.)

His style was a good fit for what producers had in mind here. When a Minnesota public broadcaster approached the TV documentary veteran Stephen Ives about doing a show for the 225th anniversary of the Constitution, the New York-based director knew that Sagal, outspoken and joke-cracking but with a dilettantish curiosity, was the logical choice.

The two then drew up plans for the show, right down to the mode of transport. (They originally imagined a bus with the Constitution painted on its side, rock-band style, but eventually settled on a custom Harley adorned with the Stars-and-Stripes that Sagal rides, sometimes uneasily.) They sought to find the right tone for a show that would lure in non-PBS viewers but play on PBS.

"We didn't want a point-counterpoint. You know, where one guy comes out and talks about eminent domain and the other comes out and gives the other perspective," Ives said. "That's a recipe for stultifying television. We wanted provocative, interesting stories told by people in their own words."

But if there's a desire to entertain, there is also an interest in showing these issues' murky complexities. No matter one's politics, the cases raise constitutional questions that are far from clear. Sagal and Ives say they're not simply trying to validate the (likely liberal-leaning) audience's opinion about hot-button issues; rather, they're trying to show that most opinions have reasonable legal roots.